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Aging of the Inconel 718 alloy between 500 and 750 °C

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Abstract

The aging of the NC 19 Fe Nb alloy (Inconel 718), previously quenched from 990 °C, is characterized by a hardness peak at 650 °C, then a maximum in hardness at about 750 °C. Over this temperature, the hardness progressively decreases. In the 550–650 °C temperature range, TEM observations have revealed that ß (Ni3Nb) precipitates are formed as long platelets parallel between them within the same grain, as well as extremely fine γ′[Ni3(Ti, Al)] particles responsible for the observed improvement in hardness. For a tempering temperature higher than 650 °C, a first hardening occurs after a 4 h treatment, which has been associated with the γ′ phase precipitation, with a more or less spherical shape. Beyond this time, a second hardening takes place linked to the γ″ phase precipitation (Ni3Nb, bct D022 structure), as thin platelet shaped, perfectly coherent with the matrix. The misfit between the γ and γ″ phases is about 3% in the 〈001〉 γ″ direction and lower than 1% in the 〈100〉γ″ and 〈010〉γ″ directions. During a longer aging at 750 °C, the γ″ platelets progressively dissolve while ß precipitates grow.

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Authors and Affiliations

  1. Laboratoire de Structure des Matériaux Métalliques, Université de Paris-Sud, Bâtiment 414, 91405, Orsay Cedex, France

    C. Slama & G. Cizeron

  2. Laboratoire de Métallurgie Structurale, URA CNRS 1107, Université de Paris-Sud, Bâtiment 414, 91405, Orsay Cedex, France

    C. Servant

Authors
  1. C. Slama
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  2. C. Servant
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  3. G. Cizeron
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Slama, C., Servant, C. & Cizeron, G. Aging of the Inconel 718 alloy between 500 and 750 °C. Journal of Materials Research 12, 2298–2316 (1997). https://doi.org/10.1557/JMR.1997.0306

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  • DOI: https://doi.org/10.1557/JMR.1997.0306

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